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Fix malloc&memcpy issue in exec_am_broadcast #203

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Merged
merged 4 commits into from
Mar 29, 2025
Merged

Fix malloc&memcpy issue in exec_am_broadcast #203

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a0e1c71
Include arpa/inet.h instead of sys/endian.h
Grimler91 Mar 17, 2025
530f292
termux-api: free malloc'ed child_argv array on execv error
Grimler91 Mar 26, 2025
512a252
termux-api: handle malloc errors
Grimler91 Mar 26, 2025
0edd4d4
Fixed: only malloc as many bytes as are actully needed
agnostic-apollo Mar 26, 2025
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26 changes: 19 additions & 7 deletions termux-api.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/endian.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
Expand Down Expand Up @@ -246,8 +246,19 @@ _Noreturn void exec_am_broadcast(int argc, char** argv,
// Close stdin:
close(STDIN_FILENO);

int const extra_args = 15; // Including ending NULL.
char** child_argv = malloc((sizeof(char*)) * (argc + extra_args));
const int child_pre_argc = 14;
const int child_post_argc = argc - 1; // Except `argv[0]`.
const int child_argc = child_pre_argc + child_post_argc;

size_t child_argv_size = (sizeof(char*)) * (child_argc + 1); // Including trailing `NULL`.
// Do not directly cast, otherwise can trigger null pointer dereference if `NULL` is returned.
void* result = malloc(child_argv_size);
if (result == NULL) {
perror("malloc failed for am child args");
exit(1);
}

char **child_argv = (char **) result;

child_argv[0] = "am";
child_argv[1] = "broadcast";
Expand All @@ -264,17 +275,18 @@ _Noreturn void exec_am_broadcast(int argc, char** argv,
child_argv[11] = input_address_string;
child_argv[12] = "--es";
child_argv[13] = "api_method";
child_argv[14] = argv[1];

// Copy the remaining arguments -2 for first binary and second api name:
memcpy(child_argv + extra_args, argv + 2, (argc-1) * sizeof(char*));
// Copy the remaining arguments except `argv[0]`, `argv[1]` should be `api_method` extra value:
memcpy(child_argv + child_pre_argc, argv + 1, child_post_argc * sizeof(char*));

// End with NULL:
child_argv[argc + extra_args - 1] = NULL;
child_argv[child_argc] = NULL;

// Use an a executable taking care of PATH and LD_LIBRARY_PATH:
execv(PREFIX "/bin/am", child_argv);

// We should not reach here, if we do, then free memory we malloc'ed
free(child_argv);
perror("execv(\"" PREFIX "/bin/am\")");
exit(1);
}
Expand Down